This invention relates to a photographic black-and-white reversal first developer which is substantially free from hydroquinone but which nevertheless provides very good development results. German application No. 197 42 490.2 filed Sep. 26, 1997 is incorporated by reference for all purposes.
Black-and-white reversal development comprises at least the following steps: first development, bleaching, clarifying, second exposure, second development and fixing. In addition, there are usually washing steps between the various chemical baths, a finishing bath and a drying step.
During the development of black-and-white reversal films, first developers are generally used which contain mixtures of hydroquinone/phenidone or hydro-quinone/metol as the developing substances.
However, hydroquinone is undesirable for health-related and environmental reasons. The object was therefore to identify a developer which is free from hydroquinone. In this respect, the object was to replace hydroquinone as a developing substance in a first developer of a black-and-white reversal process, without having to accept differences in the resulting image which are far too great.
The black-and-white first development of the reversal process is usually conducted at 20xc2x0 C. So as to be able to maintain this low temperature, cooling with cold water has to be employed, particularly in hot seasons and in hot countries. This results in high costs and in an unwanted waste of cooling water.
It is not possible to use the known black-and-white first developer at higher temperatures, since this results in an altered gradation curve and in considerably reduced maximum densities, due to subsequent development and due to a considerable increase in fogging during first development.
A second object was therefore to make black-and-white first development possible at higher temperatures.
In the reversal process, the gradation for a reversal film is fixed during first development. A good gradation during first development results in quite clear light regions and high maximum densities after reversal development.
For this purpose it is necessary that in the first development step (in contrast to pure negative development) complete development throughout is achieved of the exposed silver halide grains, so that completely clear light regions are obtained after reversal development.
At the same time, the first development must not be too active and thereby result in an increase in fogging, since this results in decreased maximum densities after reversal development.
Compounds such as amidol, catechol, hydroquinonesulphonic acid or ascorbic acid are known as alternative developer substances instead of hydroquinone in black-and-white developers.
However, the simple replacement of hydroquinone by one of these substances leads to considerably inferior results.
Surprisingly, it has now been found that the replacement of hydroquinone by hydroquinonesulphonic acid results in a developer of good quality if the black-and-white reversal first developer contains certain other substances.
The present invention therefore relates to a photographic black-and-white reversal first developer which is substantially free from hydroquinone, characterised in that it contains at least the following substances a) to d):
a) hydroquinonesulphonic acid,
b) a polyglycol with a weight average molecular weight of 200 to 600,
c) an anti-fogging agent, and
d) an auxiliary developer.
A polyethylene glycol with a weight average molecular weight of 200 to 400 (denoted as P 200 or P 400) is preferably used as the polyglycol.
5-alkylbentriazoles such as 5-ethyl- and 5-propylbenztriazole, particularly 5-methyl-benztriazole, are preferably used as anti-fogging agents.
4,4-dimethyl-1-phenyl-3-pyrazolidone (dimezone), 4-methyl-4-hydroxymethyl-1-phenyl-3-pyrazolidone (dimezone S), 1-phenyl-3-pyrazolidone (phenidone) or 4-methyl-1-phenyl-3-pyrazolidone (phenidone Z) are preferably used as auxiliary developers.
The photographic black and white reversal first developer is characterized in that in the ready to use developer the hydroquinonesulphonic acid is
a) used in the concentration of 0.01 to 0.5 moles/1,
b) the polyglycol is used in a concentration of 0.1 to 15 g/l,
c) the anti-fogging agent is used in a concentration of 1xc3x9710xe2x88x926 to 3xc3x9710xe2x88x923 moles/l, and
d) the auxiliary developer is used in a concentration of 0.001 to 0.05 moles/l.
In addition, the photographic black-and-white reversal first developer additional can contain a water-soluble rhodanide which can be used in amounts of 1xc3x9710xe2x88x923 to 1xc3x9710xe2x88x921 moles/l. The invention further describes a process for the reversal development of exposed black-and-white materials comprising at least the steps of the first development, bleaching, clarifying, second exposure, second development and fixing, and wherein a developer is used as the first developer which is substantially free from hydroquinone and which contains the following substances a) and d):
a) hydroquinonesulphonic acid,
b) a polyglycol with a weight average molecular weight of 200 to 600,
c) an anti-fogging agent, and
d) an auxiliary developer.
This process is carried out wherein the primary development is conducted at 24 to 38xc2x0 C.
The expression xe2x80x9csubstantially free from hydroquinonexe2x80x9d means that the black-and-white reversal first developer according to the invention contains less than 10% of the amount which was customary hitherto. The developer according to the invention is preferably free from hydroquinone.